An injector-type atomizer includes a cylinder and a piston and is used as a medical instrument for spraying a medicament, which has been drawn into the cylinder, from a spray nozzle at a front end of the cylinder by pressing the piston.
For a vaccine against the virus communicable through the air such as the influenza virus, it is considered most effective to be applied to the nasal mucous membrane which is infected first. Also, it has been found that the vaccine is effective even if it is sprayed to one's nasal mucous membrane instead of being injected into one's vein as has conventionally been so. Thus, the atomizer method is especially preferable for infants, since it does not cause any pain.
A conventional injector-type atomizer has a structure for merely pushing out a medicament drawn into the cylinder, and ordinarily the cylinder is filled with one dosage of the medicament. There is another type of atomizer in which several dosages of medicament are drawn into the cylinder at a time, and the medicament is sprayed dividing it into several dosages. However, a dosage of medicament sprayed (pushed out) at a time is adjusted at a rough estimate or a rule of thumb of a user, so that the user is required to get well accustomed to its use. For example, in applying a vaccine it is important to determine the dosage accurately.
Japanese Patent Laid-Open Publication No. 5-192402 discloses an injector in which a piston rod is formed with several grooves, and the distal end of a pin pushed out by a spring on the cylinder side is engaged with these grooves so that the piston rod is moved stepwise. According to the injector, a solution in the injector can be injected into an objective container surely and accurately by a regular amount by taking several actions. However, in order to make the rod to move stepwise, additional members such as springs and pins, and an additional process for providing the rod with grooves are needed to cause the increase in the manufacturing cost of the injector. Moreover, as the pin which is urged by the spring pushes the rod from one side, the rod is liable to be deformed. For this reason, the movement of rod becomes unstable, and removal and refitting of the pin fitted in the groove is troublesome in using. It is noted that the injector disclosed in the above publication is not an atomizer for spraying a medicament.